1. Field of the Invention
The present invention relates to an insertion instrument in which a rotating member rotatable around a rotation axis is provided in an insertion section. Additionally, the present invention relates to an insertion device including the insertion instrument, and an assistance tool attached to the insertion section of the insertion instrument.
2. Description of the Related Art
International Publication No. 2013/038720 discloses a spiral unit (assistance tool) which is attached to an insertion section of an endoscope (insertion instrument). The spiral unit is detachably attached to the insertion section in a state of covering the insertion section from the outer peripheral side, and includes a spiral fin spirally extending around a longitudinal axis. In the insertion section, a rotating tubular member is attached to a base portion in a rotatable state around the longitudinal axis. Furthermore, to the rotating tubular member, rollers (rotating members) are attached, and each of the rollers is rotatable (turnable) relative to the rotating tubular member around a turning axis (roller axis) as a rotation axis (center). In the insertion section, a protrusion (first projection) which protrudes toward the outer peripheral side of the insertion section is formed owing to the presence of the roller (first roller), and in the spiral unit, there are provided projections (second projections) which protrude toward the inner peripheral side. The rollers and the rotating tubular member are covered, from the outer peripheral side, with a cover tube forming a part of the outer peripheral surface of the insertion section.
In a state where the spiral unit is attached to the insertion section, the rotating tubular member and the rollers rotate together around the longitudinal axis by the transmission of driving force thereto, whereby press force around the longitudinal axis acts on the corresponding projection of the spiral unit from each of the protrusions of the insertion section via the cover tube. Consequently, the driving force is transmitted to the spiral unit, and the spiral unit rotates relative to the base portion around the longitudinal axis. In this instance, each of the rollers forming the corresponding projection turns around the roller axis. Thus, friction between the projection (roller) and the cover tube decreases.